1. The nuclear activity of late-type galaxies in the Virgo Cluster
Università degli Studi di Milano – Bicocca
Dipartimento di Fisica
Università degli Studi dell’Insubria
Dipartimento di Fisica e Matematica
Roberto Decarli
The nuclear activity of late-type galaxies in the Virgo Cluster
G. Gavazzi M. Colpi I. Arosio C. Bonfanti L. Cortese A. Boselli
Santiago, September, 6th, 2007

3. The sample The Virgo Cluster: is near us is rich is widely studied
We select all spiral galaxies in the Virgo Cluster Catalogue (Binggeli et al., 1985, 1993) with mph ≤15.
Among the complete sample of 237 galaxies:
213 (90%) have a spectroscopic classification for their nuclear activity
216 (91%) have NIR imaging
199 (84%) have r-band imaging

4. The AGN unified model
The SMBH influence radius is defined as the radius at which potential energies of the galaxy and of the massive BH are equal:
The line emission near the SMBH is Doppler broadened because of the gas fast motion (>1000 km/s!) due to the SMBH potential well (Broad Line Region)
Lines produced outside Rinf are sensitive only of the galactic potential well (Narrow Line Region)

5. Line flux ratios and nuclear activity
Gas emission line fluxes depend on gas temperature, density, metallicity and on the intensity and energy distribution of the incident radiation field
Comparing line intensities one can infer information about the ionization source and its strength
VCC 664
Stasinska, 2006
AGNs
HII-regions

6. Spectroscopic datasets
Fluxes published in Ho, Filippenko & Sargent (1997) – 40 (40)
SDSS spectra – 84 (73)
Nuclear spectra – 29 (13)
Modified drift scan spectra – 22 (4)
Drift scan spectra– 193 (81)
Nuclear activity classification in NED – 41 (2)
February-March, observing runs in Loiano +
GOLDMine database (
SDSS fiber
Slit
Nuclear spectra
Drift scan spectra
Modified drift scan spectra

7. [NII] /H and [OIII] /H
AGNs have [NII]/H > 0.6
[OIII]/H > 3 when a strong ionization field is present (Seyfert-like AGN or intensely star-forming region)
0.4 < [NII] /H < 0.6 for Transition objects
The [NII]/H ratio provides a nuclear activity classification without any further information

8. 56 AGNs (23. 6%): - 9 Seyfert (3. 8%) - 23 Seyfert/LINERs (9
56 AGNs (23.6%): - 9 Seyfert (3.8%) Seyfert/LINERs (9.7%) LINERs (10.1%)
21 Transition objects (8.9%)
121 HII-Regions (51.1%)
15 No Emission Line Galaxies (6.3%)
24 No spectra available (10.1%)

9. Dynamical mass and H-band luminosity
Mdyn = dynamical mass up to the optical radius of the galaxy
Direct measures of Mdyn are observational time consuming
For spiral galaxies:
(Gavazzi et al., 1996)
We use H luminosity as a surrogate of Mdyn. NIR data were taken from 2MASS and from GOLDMine databases
Adapted from Gavazzi et al. (1996)

10. Mass distribution
Only VCC 213 has Mdyn<1010 Mo and hosts an AGN
AGN fraction changes from 0% up to 100% when Mdyn changes between ∽1010 Mo and ∽3·1011 Mo (see also Kauffmann et al., 2003)
Mdyn > 1010 Mo is a necessary condition for harbouring an AGN
Mdyn > 3·1011 Mo is also a sufficient condition

11. The colour-magnitude diagram
The AGN host galaxies are usually found to be redder than non-active galaxies.
Some authors (e.g., Obric et al., 2006) suggested that the AGN feedback may be responsible of this effect.
AGNs populate the high-mass end of the same colour- magnitude relation as the one observed for inactive galaxies!

12. The role of bulges
From NIR light profile we define:
Bulge dominated galaxies have C31>4
Pure disks have C31∽2.5
When Mdyn> 1011 Mo, both bulge- and disk- dominated spiral galaxies are found (see Gavazzi Pierini & Boselli, 1996; Scodeggio et al., 2002)
Bulge-dominated spiral galaxies
AGNs are found in all the galaxies having prominent bulges, but even in bulgeless galaxies!
Disk-dominated spiral galaxies

13. M100
M61
NGC4535

14. AGNs are found mainly at high values of Nuc
Light cusps
Sensitive to unresolved nuclei and light cusps
Nuc increases continuously with Mdyn
AGNs are found mainly at high values of Nuc

15. Are r-band nuclei the due to AGN continuum?
Nuclear spectra of 4 AGNs in our sample were observed with HST (Spinelli et al., 2006). All of them are well fitted with Bruzual & Charlot libraries of star spectra.
AGN continuum light is thus negligible with respect to the stellar component.
VCC Seyfert
VCC LINER
VCC Seyfert
VCC LINER

16. Environment – I
We divide our sample in two parts, according to the angular separation of the galaxies from M87:
High density subsample: galaxies, 37 AGNs (32±8 %)
“Low” density subsample: galaxies, 40 AGNs (40±10 %)
The mass distribution of the subsamples are similar.
The observed AGN fractions are consistent.

17. The environment does not significantly influence the nuclear activity
Environment – II
We check the [NII]/Ha dependence on the neutral gas deficiency (Haynes & Giovanelli, 1984).
Even considering the HI deficiency no clear environmental effect is observed, once the luminosity dependence is taken into account.
The environment does not significantly influence the nuclear activity

18. What can we argue about the BH-host galaxy joint evolution?
At least in spiral galaxies, the nuclear activity is strongly sensitive to the host galaxy mass, while the morphology plays a secondary role.
The environment is not relevant in nuclear activity.
There is no evidence of a strong feedback mechanism in the galaxy colours.
Low accretion rates are observed.

19. The massive BH may have grown simultaneously with the galaxy, in an anti-hierarchical way:
The dynamical mass is the driver of both the galaxy and the BH growth, in a top-down scenario
The scale relations inset during the formation itself of the system
Galaxies do not require any strong feedback later on, neither strong accretion rates
The “fragile” morphology of pure disk and bulgeless galaxies is preserved, since the BH is already formed

20. Bibliography
Decarli, Gavazzi, Arosio, Cortese, Boselli, Bonfanti, Colpi, 2007, arXiv: , accepted for publication in MNRAS
Ferrarese, 2006, in Series in High Energy Physics, Cosmology and Gravitation, `Joint Evolution of Black Holes and Galaxies', ed. by M. Colpi, V. Gorini, F. Haardt, U. Moschella (New York - London: Taylor & Francis Group), 1
Gavazzi, Pierini & Boselli, 1996, A&A, 312, 397
Gavazzi, Boselli, Scodeggio, Pierini & Belsole, 1999, MNRAS, 304, 595
Gavazzi, Boselli, Donati, Franzetti & Scodeggio, 2003, A&A, 400, 451
Haynes & Giovanelli, 1984, AJ, 89, 6
Kauffmann et al., 2003, MNRAS, 346, 1055
Kauffmann & Heckman, 2005, RSPTA, 363, 621
Lequeux et al., 1979, A&A, 80, 155
Marconi & Hunt, 2003, ApJ, 589, L21
Obric, et al., 2006, MNRAS, 370, 1677
Scodeggio, Gavazzi, Franzetti, Boselli, Zibetti, Pierini, 2002, A&A, 384, 812
Veilleux, et al., 2003, AJ, 126, 2185

22. Correcting for line absorptions
Balmer lines are usually observed both in emission and in absorption
When possible, both the emission and absorption features are fitted. Otherwise, a correction is applied assuming various templates according to the galaxy luminosity.

23. Spectroscopic datasets
Fluxes published in Ho, Filippenko & Sargent (1997) – 40 (40)
SDSS spectra – 84 (73)
Nuclear spectra – 29 (13)
Modified drift scan spectra – 22 (4)
Drift scan spectra– 193 (81)
Nuclear activity classification in NED – 41 (2)
February-March, observing runs in Loiano +
GOLDMine database (
Slit
Drift scan spectra
Nuclear spectra
Modified drift scan spectra
SDSS fiber

25. The [NII]/Ha ratio along the slit

26. The Narrow Line Region size
For a subsample of AGNs, we extract the [NII]/Ha ratio at various apertures, up to some kpc
Only in one galaxy (VCC 73) the ratio significantly descreases in the first kpc
Veilleux et al., 2003
Thus, the photoionization of an AGN extends up some kpc!

27. Mass dependence
The [NII]/H ratio increases with the dynamical mass of the host galaxy
A bimodality is observed:
In low-mass host galaxies, the [NII]/H ratio is a metallicity indicator:
At higher masses, a further contribution to the [NII]/Ha ratio is provided by the AGN
AGN
metallicity

28. Black hole masses
Only few tens ‘direct’ supermassive BH mass measures are available, mostly in elliptical galaxies (see Ferrarese, 2006 for a review)
Following Marconi & Hunt (2003), the MBH of our sample AGNs is estimated from the bulge NIR luminosity:
All the BHs in our sample have MBH>105.8 Mo.

29. The accretrion rate L/LEdd
The accretion rate is usually identified with the ratio between the AGN bolometric luminosity and the BH Eddington luminosity:
Most of our objects have very low accretion rates
The AGN bolometric luminosity is roughly proportional to the [OIII] luminosity (Heckman et al., 2004).
We thus have an order-of-magnitude estimate of L/LEdd for our objects.

30. Summarizing…
Mdyn>1010 Mo is a necessary condition to harbour an AGN
The AGN fraction steeply rises with the dynamical mass, and it is virtually 1 when Mdyn>3·1011 Mo
AGNs are found even in a number of bulgeless galaxies
Nuclear stellar cusps are often found in AGN host galaxies
The same colour-magnitude relation describes both active and inactive galaxies
No significant environmental dependence of the nuclear activity is observed
All the AGNs in our sample have MBH>105.8 Mo
Very low accretion rates are found in almost all our targets